This invention relates to a cylinder discriminating sensor layout and more particularly to an improved arrangement for providing a signal indicative of the phase relationship of an internal combustion engine.
As is well known, many controls for an internal combustion engine are dependent upon the phase angle of the output shaft of the engine. Where multiple cylinder engines are employed, it is also necessary to determine not only the phase angle of the output shaft but which cylinder is at its top dead center position at a given point in time. Alternatively, a reference signal is generated when one cylinder of the engine is at top dead center so that the control system can discriminate which cylinder is firing at a given phase angle of the engine output shaft.
Sensors of the aforenoted types are normally mounted in proximity to the output shaft of the engine. However, such measurements directly from the engine output shaft have some disadvantages. The first of these disadvantages is that the crankshaft of the engine is normally a relatively inaccessible component and if the sensors are mounted in proximity to the crankshaft they also become inaccessible. Furthermore, it is very difficult to check the conditions of these sensors and/or the wire leads leading to them when such remote positioning is employed.
In addition to these disadvantages, when the engine operates on a four stroke cycle, not only is it necessary to determine when a given cylinder is at its top dead center position but also whether this cylinder is at top dead center at a time when it is fired or when it is merely completed the end of its exhaust stroke and the beginning of the next intake stroke. This problem may be avoided by operating the sensors off of another shaft that is driven from the crankshaft at one half engine speed. However, such additional shaft drives not only complicate the construction but also give rise to problems in where the sensors will be located.
It is, therefore, a principal object to this invention to provide a cylinder discriminating sensor layout for an internal combustion engine wherein the sensor is positioned in a readily accessible area.
It is a further object to this invention to provide a cylinder discriminating sensor layout for an internal combustion engine wherein the sensor cooperates with a shaft of the engine which is normally driven at one half engine output shaft speed but which does not require the use of an auxiliary shaft solely for the sensor.
It is a further object to this invention to provide an improved mounting arrangement for an internal combustion engine sensor that places the sensor in an easily accessed position and also places the sensor where it can not be contaminated and the leads going to it can be readily inspected.
A further problem with sensors of the afornoted types is that the mounting of not only the sensor but also the element on the shaft with which it cooperates is critical. That is, if the sensor is not mounted accurately, then the timing positions will be incorrect. Furthermore, sensors of the types previously proposed have required the provision of a sending element that is fixed to the shaft with which the sensor cooperates. If this element is not correctly positioned on the shaft, timing errors can also result.
It is, therefore, a further object to this invention to provide an improved sensor arrangement for an engine wherein the sensor can cooperate with an element of the engine rather than a separate part which must be fixed to an element of the engine.
It is well known in four cycle engines to drive the camshafts at one half engine speed. Therefore, the camshafts themselves provide a readily accessible shaft which is driven at one half engine speed and which can provide the necessary sensor arrangement without necessitating an additional shaft. However, sensor arrangements that cooperate with engine camshafts have, heretofore, required the provision of an additional element on the camshaft to cooperate with the sensor to provide a signal.
It is, therefore, a still further object to this invention to provide an improved sensor arrangement for an internal combustion engine wherein the sensor signals are derived directly from a cam lobe of the camshaft.
A further disadvantage of previously proposed sensor arrangements for cooperation with the camshafts of engines has been that the sensor itself has been mounted either within the cam cover of the engine and/or on some element that places the sensor in a awkward or difficult place to access, such as the cylinder head or the like.
It is, therefore, a still further object to this invention to provide an improved sensor arrangement for cooperation with the camshaft and wherein the sensor is carried directly by the cam cover of the engine.